Armature for an actuator with a flux guide therearound



1970 r F. D. MILES I 3,523,271

ARMATURE FOR AN ACTUATOR WITH A FLUX GUIDE THEREiAROUND Filed June 27. 1968 INVENTOR. F. D. M/(fiS A TTOE/VG United States Patent O M 3,523,271 ARMATURE FOR AN ACTUATOR WITH A FLUX GUIDE THEREAROUND Floyd Delbert Miles, Santa Clara, Calif., assignor to International Telephone and Telegraph Corporation, New York, N.Y., a corporation of Delaware Filed June 27, 1968, Ser. No. 740,596

1 Int. Cl. H01f 7/08 US. Cl. 335-230 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic actuator for a vacuum switch or the like. The actuator has an armature with a flux guide therearound. The armature has a thinned portion so that it may be bent to shape for adjustment purposes. The flux guide shunts magnetic flux around the thinned portion. An actuating arrangement is also provided to cause the armature to toggle to one of two positions by the application of a momentary voltage to one of two corresponding solenoids. A permanent magnet holds the armature in one position. The magnet does not have a field strength sufiicient to overcome the force of a spring which biases the armature in the other position. A first solenoid is then provided to aid the magnet. A second solenoid bucks the magnet to allow the spring to return the armature.

BACKGROUND OF THE INVENTION This invention relates to electromagnetic actuators, and more particularly to devices for actuating doublethrow vacuum switches or the like.

In the past it has been very difiicult to adjust properly the position of the armature of very small electromagnetic actuators. Further, no satisfactory actuator has been provided to toggle to one of two positions with momentary applications of electrical power.

SUMMARY OF THE INVENTION In accordance with the device of the present invention, the above-described and other disadvantages of the prior art are overcome by providing an actuator armature having a thinned or necked-down portion so that the armature may be bent for adjustment purposes.

In accordance with one feature of the invention, flux guide is employed to provide a low reluctance magnetic shunt path around the thinned portion of the armature.

It is another feature of the invention that an actuator is provided that toggles to either one of two positions with the momentary application of electrical power. This actuator has a permanent magnet to hold the armature against the force of a spring. An aiding solenoid helps the spring force to be overcome. A bucking solenoid either partially or totally overcomes the field of the magnet to allow the spring force to become dominant.

The above-described and other advantages of the present invention will be better understood from the following description when considered in connection with the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWING In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a longitudinal sectional view of an actuator constructed in accordance with the present invention; and

FIG. 2 is a transverse sectional view of a portion of the actuator taken on the line 2-2 shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In 'FIG. 1, the actuator of the invention is indicated at 10 connected to a vacuum switch 11. Vacuum switch 11 is disclosed in co-pending application, Ser. No. 725,645, filed on May 1, 1968 by F. Miles for Vacuum Switch Structure.

Briefly, vacuum switch 11 has fixed contacts 12 and 13 which are engaged by movable contacts 14 and 15 on a rod 16. Rod 16 is fixed to the center of a circular flexible diaphragm 17. Rod 16 has an enlarged integral portion 18 below diaphragm 17, around which a cylindrical insulator 19 is located. An insulator rod 20 is located inside insulator 19. Insulator 19 is oscillated back and forth by an armature 21 of actuator 10, having a ring 22 fixed thereto. Ring 22 extends around insulator 19.

Armature 21 is pivoted about a pin 23 that extends through two legs, 24 and 25 of a U-shaped flux guide 26, as shown in FIG. 2.

Actuator 10 also includes a permanent magnet 27 which extends around flux guide 26 at the upper end thereof, as viewed in FIG. 1. Magnet 27 is radially polarized.

A bucking coil 28 is wound on the upper end of a nonmagnetic cylindrical bobbin 29. An aiding coil 30' is wound on the lower end of the bobbin.

Coils 28 and 30 are surrounded by a non-magnetic housing 31.

Actuator 10 includes a non-magnetic case 32 which is fixed to vacuum switch 11. Actuator 10 has a magnetic case 33 inside case 32. Case 33 has a projection 34 against which the lower end of armature 21 abuts in one position of switch 11. In its other position, the lower end of armature 21 is spaced from projection 34. A ferromagnetic bar 35 is positioned adjacent projection 34 to increase the amount of magnetic material thereat.

Actuator 10 has a non-magnetic end cover 36.

A leaf spring 37 biases armature 21 in a direction to space the lower end thereof from projection 34.

In the operation of actuator 10 when the lower end of armature 21 is spaced from projection 34, spring 37 is sufficiently strong to prevent magnet 27 from rotating armature 21 to the right about pin 23. If coil 30 is energized, armature 21 will assume the position shown in FIG. 1. Coil 30 need be energized only momentarily, and magnet 27 will keep armature 21 in the position shown.

Should it be desirable to rotate armature 21 back to a position such that its lower end is spaced from a projection 34, coil 28 is energized to cancel the field of magnet 27 either partially or totally. Spring 37 will then return armature 21 to the position in which its lower end is spaced from projection 34. In this case, as before, coil 28 need be energized only momentarily.

Note will be taken that armature 21 has a thinned portion at 38 so that it may be bent to shape for adjustment purposes. Flux guide 26 provides a low reluctance path around thinned portion 38 for magnetic flux. Except for thinned portion 38, armature 21 may have a square cross-section uniform throughout its length.

Man changes and modifications of the invention will suggest themselves to those skilled in the art. The embodiment shown and described has been selected for purposes of illustration only. The invention is, therefore, not to be limited to the embodiment selected for this disclosure, the true scope of the invention being defined only in the appended claims.

What is claimed is:

1. An electromagnetic actuator comprising: a ferromagnetic armature having a thinned portion at a point intermediate its ends, a magnetic circuit having a projection to contact said armature; said magnetic circuit including an elongated U-shaped ferromagnetic flux guide extending around at least three sides ofsaid armature to bypass magnetic flux around said thinned portion of said armature; a permanent magnet to retain said armature against said projection; said permanent magnet having a field strength insuiiicient to pull said armature toward said projection from a position spaced therefrom; spring means to bias said armature away from said projection; a first solenoid winding adapted to pull said armature to said projection; and a second solenoid winding wound in a direction and adapted to cancel the field of said permanent magnet to such an extent such that said spring means can return said armature to a position spaced from said projection.

2. The invention as defined in claim 1, wherein said armature has two parallel, flat surfaces along its length, said armature being pivoted about an axis perpendicular to said surfaces, said flux guide having two legs with internal fiat surfaces contiguous to those of said armature, said armature having a uniform thickness between said flat surfaces thereof along the length thereof where said thinned portion is located.

3. The invention as defined in claim 2, wherein said magnet is annular in shape and is positioned around one end of said armature, the other end of said armature being adapted to contact said projection, said second solenoid being positioned around said armature adjacent said magnet, said first solenoid being positioned around said armature adjacent said second solenoid, said magnetic circuit including a cylindrical shell surrounding said magnet and both of said solenoids, said projection extending from said shell at the end of said first solenoid opposite the end adjacent said second solenoid.

4. The invention as defined in claim 3, wherein said 4 flux guide is positioned around said armature inside of said magnet and inside of both of .said solenoids.

5. The invention as defined in claim 1, wherein said magnet is annular in shape and is positioned around one end of said armature, the other end of said armature being adapted to contact said projection, said second solenoid being positioned around said armature adjacent said magnet, said first solenoid being positioned around said armature adjacent said second solenoid, said magnetic circuit including a cylindrical shell surrounding said magnet and both of said solenoids, said projection extending from said shell at the end of said first solenoid opposite the end adjacent said second solenoid.

References Cited UNITED STATES PATENTS 2,276,535 3/1942 Clare et al. -1 335-230 2,391,692 12/1945 Estes 335276 XR 3,071,714- l/l963 Hadekez 335-227 3,154,728 10/1964 Bordenet 335-236 XR 3,161,806 12/1964 Gordon 335230 XR FOREIGN PATENTS 983,303 2/1965 Great Britain.

GEORGE HARRIS, Primary Examiner Us. 01. X.R. 335-237, 279 

